An optical amplitude modulation method suitable for a CVQKD system

Abstract

The invention discloses an optical amplitude modulation method suitable for a CVQKD system. The modulation method comprises an optical isolator, a polarization-maintaining optical coupler BS, a phasemodulator PM and a delay optical fiber DL. Only two passive devices (an optical loop and a 2*2 optical coupler) and a phase modulator are needed to modulate the amplitude of the optical signal precisely by using the special structure of an optical fiber Sagnac (Sagnac) loop. As that amplitude modulation method of the invention does not have the bias drift of the working point when the amplitude ismodulate, the modulation accuracy is high, and the external feedback control is not needed at the same time, the realization structure is simple, the cost is low, and the requirement for the modulated signal is low. This method is especially suitable for amplitude modulation of quantum optical signals in continuous variable quantum cryptosystems. It can greatly improve the stability of continuousvariable quantum key distribution system and greatly promote the practical application of continuous variable quantum cryptosystems.

Description

technical field [0001] The invention relates to an optical amplitude modulation method suitable for a continuous variable quantum cryptography system. Background technique [0002] In continuous variable quantum key distribution systems, accurate amplitude modulation of quantum signal light is a key technology for quantum state signal preparation. The modulation accuracy directly determines the accuracy of Gaussian modulation, which has a major impact on system security. The traditional method is to use a lithium niobate Mach-Zehnder intensity modulator (LN-MZM Amplitude Modulator, AM) to modulate the amplitude of the signal light. However, due to factors such as environmental changes, device aging, stress, and external electric field, the initial bias point of the intensity modulator itself will slowly change with time. The drift of the bias operating point of the intensity modulator will cause a large deviation between the amplitude value actually loaded on the modulation...

AI Technical Summary

Problems solved by technology

Due to the first limitation of the technology level and the physical structure of the device, the intensity modulator itself will have a shift in the operating point, which will reduce the accuracy of the modulation, which in turn will affect the security code rate of the system. When the drift is too large, it will even make communication impossible.

In order to avoid the impact of modulator operating point drift, the feedback bias control system is usually used for real-time monitoring and compensation, but this method will increase the complexity of the system, and at the same time, the monitoring pilot signal introduced for monitoring and feedback will also affect the required The transmitted signal will affect the signal-to-noise ratio of the system

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